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Biomedical subjects

H Takano

Publications and source records attributed to H Takano.

At least 487 records · Page 27Linked to original sources
PubMed1985

Mechanical stability of elastomeric polymers for blood pump applications.

As a series of studies on the mechanical properties of materials used in cardiac prostheses, static and dynamic characteristics and stability of five kinds of elastomeric polymers have been studied by uniaxial tensile and fatigue tests in air at room temperature and in saline solution at 37 degrees C. Of all materials tested in this study, Texin MD85A, a segmented polyether polyurethane, has the lowest flexibility under static and dynamic conditions, with relatively high strength. Hexsyn, a polyolefin rubber, is highly flexible with little stress relaxation. However, this material has very low tensile strength and short elongation, and shows unstable change in the elastic modulus during cyclic deformation. Avcothane 51, a copolymer of polyurethane and silicon, has unstable mechanical properties and gradually stiffens upon cyclic deformation. On the other hand, Biomer, a segmented polyether polyurethane, has high flexibility and shows the most stable behavior during cyclic deformation regardless of test environment. Toyobo TM5, a similar segmented polyurethane to Biomer, has higher strength and ductility than Biomer, although its static and dynamic flexibility are slightly worse and less stable than those of Biomer. These results indicate that Biomer and Toyobo TM5 are more suitable for flexible components of cardiac prostheses.

Air↗
PubMed1985

Ciliary activity in patients with nasal allergies.

Nasal allergy is a disease ensuing from type-I allergic reactions in the nasal cavity. A correct understanding of this process requires further investigation of the non-allergic pathology present. In the allergic state, the function of the nasal cilia is considered to be involved in the invasion of allergens into the nasal mucosa, and may also be involved with the manifestation and progression of the disease produced. In the present study, we examined the ciliary activity of the nasal mucosa of 35 patients with nasal allergies by using the photo-electric method of Ohashi and Nakai to better understand the non-allergic pathologies present. The nasal cilia of four healthy volunteers served as controls. In addition, a multivalent analysis was made according to quantifying theory I in order to define the effects of various factors on ciliary activity in the nasal mucosa during the allergic state. The following results were found in our present study. Ciliary activity was observed in 32 of 35 patients with nasal allergy. The mean value of the ciliary activity in these patients was 498 +/- 195 beats/min, while that of the normal controls was 753 +/- 46 beats/min. The ciliary activity in the nasal mucosa in the allergic state declined as the morbid period was prolonged; this decline in ciliary activity was relatively great in cases of perennial allergies aggravated by season-specific allergens.

Adolescent↗
PubMed1985

Effects of implantation on the mechanical properties of the polyurethane diaphragm of left ventricular assist devices.

Tensile properties of blood pump diaphragms made from a segmented polyether polyurethane (Toyobo TM5) were studied after implanting in goats for variable periods of time up to 72 days. The implantation decreased the tensile strength and ultimate elongation at break, while the elastic modulus increased very slightly. These changes in the strength and ductility were primarily caused by the contact of material with blood rather than by the mechanical fatigue of material. Mechanical stability was greatly improved by removing residual oligomers from the material by a refining procedure. The refined polyurethane has characteristics favourable for blood pump applications.

Animals↗
PubMed1985

Spinal cord monitoring: basic principles and experimental aspects.

Spinal cord monitoring, based on spinal cord potentials recorded close to the conus medullaris and evoked by stimulating rostral spinal cord, has been extensively used clinically in Japan. To understand how such spinal cord evoked potentials (SCEP) reflect injurious effects on the spinal cord, we carried out the following animal experiments. The effects of spinal cord distraction, compression, and combined compression and hypotension or hypoxia were examined. We found that there is a critical point of compression or distraction of the spinal cord at which SCEP amplitude decreases significantly. Acute hypotension concomitant with moderate compression increases the risk of insult to the cord. Accordingly, we believe that repetitive monitoring and rapid feedback to the surgeon are indispensable to intraoperative spinal cord monitoring. Furthermore, hypotension should be carefully avoided whenever symptoms of spinal cord compression occur. A comparative study of SCEP and spinal SEP indicates that both potentials can substitute for each other, although the sensitivity of the SCEP for detecting hazardous effects is higher.

Acute Disease↗
PubMed1985

[Scintigraphy in the small animals using a human gamma camera--evaluation of bone scintigraphy in the rat mandible and maxilla].

In order to obtain clear scintigrams of small animals, some improvements were brought on a pinhole collimator. Then, using a human gamma camera with this collimator improved, bone scintigraphy was attempted in the rat mandible and maxilla, experimentally to examine the desirable conditions of scintigraphy. The most desirable bone scan images were obtained under the conditions that the pinhole was 1.5 mm in diameter, the distance between the collimator and the object was 0 cm, and the exposure was 400.

Animals↗
PubMed1985

Antithrombogenic elastomers: novel anticoagulant/complement inhibitor-controlled release systems.

We have introduced novel synthetic anticoagulant and complement inhibitors for controlled release systems with high biocompatibility. These drugs were molecularly designed for extremely high biospecific inhibition, are readily soluble in polar organic solvents, such that they have versatile applications in commonly used hydrophilic polymeric systems via an easily attainable one-step co-casting technique at a given amount of loading. Another characteristic feature of the controlled release system is that both release rate and duration are controlled by the material, formulation and fabrication variables. These are easily manipulated by the hydrophilicity of polymers, amount of loading and film thickness. The drug-impregnated system may generate a new dimension in the formulation of controlled release biocompatibility.

Animals↗
PubMed1985

[Morphological features of the nuclei of the principal cells in the epididymal duct in mice, with special emphasis on the regional differences in the duct and age-related changes].

The mouse epididymal duct is divided into five segments (I-V). In this study, morphological features of the nuclei of the principal cells in the epididymal duct were examined in mice from 20 to 360 days of age, with special reference to the regional differences in the duct and age-related changes. By morphological characteristics of the nuclei, the principal cells were classified into three types; the cells with a nucleus of usual size, those with two nuclei, and those with a large nucleus. Binuclear principal cells were mainly distributed in segments IV and V. They appeared at 30 days of age and increased to about 20% out of the all principal cells in segment IV and about 30% in segment V with morphological differentiation of the segment until 40 days. After 40 days, they furthermore increased in segment IV, but decreased in segment V. The cells with large nuclei are frequently seen in segments IV and V after 120 days. Especially in segment V, about 70% of the principal cells had large nuclei. The nuclei with deep invaginations of the nuclear membrane or slit figures were frequently observed after 120 days of age. The principal cells with such nuclei were rare in segment I, 10-20% in segments II-IV, and about 60% in segment V. These nuclei were similar in size to the usual nuclei in segments II and III but large in segments IV and V. In conclusion, morphological characteristics of the nuclei in the principal cells are different between the proximal and distal regions which are functionally different, and the principal cells with two nuclei and those with a deformed nucleus increase in number in relation to the functional differentiation and aging of the epididymal duct.

Age Factors↗
PubMed1984

Microvasculature of the mouse epididymis, with special reference to fenestrated capillaries localized in the initial segment.

The blood supply, microvasculature, and ultrastructure of the capillaries in the epididymis in adult mice were regionally examined. The epididymal duct of the initial segment is surrounded with a dense network of fenestrated capillaries running just under the epithelium. The other segments have loose networks of nonfenestrated capillaries running in the interductal connective tissue. The fenestration of capillaries in the initial segment was markedly reduced in frequency immediately after cutting the efferent duct. In adult mice which were subjected to cutting of the efferent duct neonatally, the dense capillary network did not develop, and fenestrated capillaries were absent in the initial segment. We interpret our results to indicate that the fenestrated capillaries in the initial segment provide for absorption of the testicular fluid and that their development is dependent upon the testicular fluid entering the epididymal duct.

Animals↗
PubMed1984

Effects of immersion in cholesterol-lipid solution on the tensile and fatigue properties of elastomeric polymers for blood pump applications.

Tensile and fatigue properties were studied on three kinds of segmented polyether polyurethanes developed for blood pump applications. To study the effects of plasma constituents, specimens were immersed in a cholesterol-lipid solution whose composition is similar to that of plasma. The results obtained were compared with those observed in a saline solution which had been reported previously. Immersion in the cholesterol-lipid solution has influence on the mechanical properties of Toyobo TM5 polyurethane and Avcothane 51: Its effect is enhanced by cyclic deformation. Cholesterol-lipids change the mechanical characteristics of Avcothane 51 more remarkably than those of Toyobo TM5 polyurethane possibly because the former contains about 10% silicone. On the other hand, there is little effect of the constituents of the cholesterol-lipid solution on the static and dynamic mechanical properties of Biomer, although moisture and cyclic deformation have some influence on the mechanical characteristics.

Assisted Circulation↗
PubMed1984

Asymptomatic leiomyosarcoma of maxillary sinus accompanied by primary mucocele.

A case of asymptomatic leiomyosarcoma of the maxillary sinus accompanied by primary maxillary mucocele is presented together with a review of the literature. The manifestation and symptoms, pathology in special reference to electron microscopic findings, treatment and prognosis, and origin of this tumor are discussed. Initially, this tumor should be treated by extensive surgical excision, but long-term follow-up is essential in the light of this high rate of local recurrence, and radical neck surgery is indicated for metastatic nodal disease.

Female↗
PubMed1984

Design of pusher-plate-type left ventricular assist device based on mechanical analyses.

A permanently implantable left ventricular assist device (LVAD) pump of the pusher-plate type was designed based on mechanical analyses. A series of three different segmented polyether polyurethanes was utilized for the diaphragm, cannulae, and their blood-contacting surfaces, considering each material's characteristics. The span and thickness of the pump diaphragm were determined so as to minimize the stress developed by the bending and blood pressure forces. The inflow and outflow cannulae were designed using fundamental equations that describe the operation of a piston-type reciprocating pump. The pump diameter was determined considering the required flow for the average Japanese person. In vitro and in vivo experiments showed good pump performance, which satisfied the design specifications. No failure was observed in the designed diaphragm. The Hall effect sensor incorporated in the pump was very useful in monitoring the cardiac output of the pump.

Animals↗